1. Technical Field
Embodiments of the invention relate to a system and method for controlling the use of multiple fuels.
2. Discussion of Art
Internal combustion engines may be classified as compression-ignition or spark-ignition engines. A diesel engine is a compression-ignition engine, and a gasoline engine is a spark-ignition engine.
Engines may be classified as either two-stroke or four-stroke. A four stroke engine includes an intake stroke, a compression stroke, a power stroke, and an exhaust stroke. During the intake stroke, the engine introduces fuel and air into a cylinder as its respective piston moves away from top dead center (TDC) in the cylinder. During the compression stroke, the piston moves toward TDC in the cylinder, thereby compressing the fuel/air mixture until ignition. The ignition occurs due to the heat of compression and/or a glow plug in a compression-ignition engine. The ignition occurs due to a spark a spark plug) in a spark-ignition engine.
For either engine type, the combustion of the fuel/air mixture causes significant heat and pressure in the cylinder during the power stroke, thereby driving the piston away from TDC and creating mechanical output power through the crankshaft, transmission, and so forth. During the exhaust stroke, the piston moves back toward TDC, thereby forcing the exhaust out of the cylinder. A two stroke engine operates by combining the power stroke with the exhaust stroke, and by combining the intake stroke with the compression stroke.
In each of these engines, a variety of parameters affect the engine performance, fuel efficiency, exhaust constituents, and so forth. Exhaust constituents include carbon oxides carbon monoxide), nitrogen oxides (NOx), sulfur oxides (SOx), unburnt hydrocarbons (HC), and particulate matter (PM). Each engine has threshold values, such as speed, flow rate, temperature, and pressure associated with the various components. For example, the threshold values may include in-cylinder peak firing pressure (PEP), pre-turbine temperature (PTT) of a turbocharger, and turbocharger speed (TRBSPD) of the turbocharger. A specific threshold value of a turbocharger is a choke line, which often represents a threshold limit in the air flow rate or pressure ratio between a compressor inlet and exit due to design constraints in the size of inlets, outlets, passages, and so forth. These engine parameters (e.g., PFP, PTT, and TRBSPD) should be maintained within a threshold value range to avoid failure of the engine power assembly and turbocharger. Also, the compressor choke condition should be avoided to reduce the possibility of turbocharger failure.
It may be desirable to have an engine and/or a controller that differs from those that are currently available. It may be desirable to have a method of operation that differs from those methods of use that are currently available.